jetstream

A Mew 180 would be great for galaxies but the limited TFOV will hinder some nebula and starfields etc. Actually Im not sure if the Mew 180 is that limited- I wonder if the scope acts as a "field stop" before 46mm is reached with an eyepiece? ie will it vignette with a 42mm LVW class eyepiece?

Everyone should have a large aperture dob IMHO, if circumstances allow. A 1/10 wave mirror, .98 Strehl is not needed- just a nice smooth 1/4 wave system is all thats needed. They really do show more of DSO than other scopes, under dark skies espc.

My 15" is a superb scope and takes higher mag than the 24", it is so easy to use- left assembled, wheeled out and collimated in 5 minutes...and it doesn't weigh over 300 lbs and need an 8 foot step ladder. Its my favourite scope actually. Mind you the 24" does things the 15" cant- planetary nebula explode in the big one and I get about 2/3 of the actual bubble arc in the Bubble nebula and more... The 15" actually renders my smaller scopes redundant, the TSA120 excepted, oh and the H130 is a keeper, another favourite scope.

One more thing before it appears as if Im hijacking your news lol! I hear Mr Nichols mirrors are smooth, a requirement in my books. Off fishing for walleye.

I find my 24" too bright on the moon and planets whereas the 15" is perfect for that role, as your 12" is. I just cant believe the difference in image "brightness" between the 15" and 24", its mind boggling. The Veil through your 20" from dark skies will make you gasp...

That is the perfect size mirror IMHO.The f3.5 will run at f 4 with the PCII and give perfect illumination and size on the DSO, Congratulations Magnus!!

@Captain MagentaWhat diameter?

Yes, Mikes build should be made a sticky or easily accessible somehow, excellent craftsmanship. As was @mapstar. His build should be highlighted too IMHO.

Yes full disclosure is a sign of honestly and allows for an informed consumer. All (?) optical glass contains bubbles and inclusions. For those interested Schott publishes the data

I say this with regard to both the loss of contrast with respect to MTF and also the loss of light due to the "bullet hole" effect 😀 I'll take a near perfect 20% obstructed scope over an un obstructed scope with 1/4 wave SA... The nice thing about large aperture newts is the ability to use small central obstructions and still get a nicely illuminated field.

APM contract with LZOS says bubbles are OK. At least they are telling us, most (all?) other manufacturers dont. "5. Bubbles and inclusions requirements Permissible dimensions of bubbles and inclusions: For systems of diameter up to 152mm In lens material bubbles and inclusions of no more than 0.3mm in size are allowable , and a number of bubbles of diameter 0.03mm to 0.3mm in each lens shall not exceed 3 pieces. For systems of more than 152mm up to 254mm diameter Number of bubbles and inclusions of size up to 0.3mm - not more than 20 pieces. - up to 0.5mm - not more than 3 pieces. Bubbles and inclusions in material exceeding the requirements above shall be coordinated on the stage of optical blanks selection for the manufacturing of each lens" https://www.apm-telescopes.de/en/telescopes/apochromatic-refraktors/apm-lzos-apo-refractors/apm-lzos-telescope-apo-refractor-130-780-3.7-inch-focuser.html

The 20% (or so) missing from the primary mirror due to obstruction is not missed...

Wait until you see your coatings start to get eaten by the dust/dew mix 😀 mind you if you don't clean it you might not know until its too late

I store my scopes in a shipping container- a "sea can". Theres a few of us that use the method - you can feel the dirt or if the mirror is clean.

When needed... sometimes 4-5 times a year but now they are in a sea can they stay much cleaner, longer. My preferred method is a soapy water spray to rinse, followed by another soapy water spray, spray the fingers and very gently use the fingers to clean the mirror. Soap is a must as it lubricates. The final rinse is with distilled or "Aquafina". This is just me, others will have different suggestions.

Some mention views through reflectors are sub par- they are like anything else, they need to be cleaned and maintained. I mean how many refractor owners have a bunch of dust on the lenses? Dust is bad- some of it is organic, mix this with dew and the mixture eats coatings...

I watch these threads trying to learn a bit from each. Whether or not an in depth understanding like @vlaiv has, is reached (most likely not) the path that these threads take us will enhance understanding and give us flexibility in image capture and processing IMHO.

I hadn't used my scopes much this winter but decided to do some "serious" DSO viewing in -30c. After wheeling the 15" out I noticed a bunch of dust on the primary... Previous views had me realize contrast was not up to par. What to do for an emergency cold weather clean with 21.8 super transparent skies available? I did a not recommended alcohol/paper towel clean. I placed paper towel on the primary (in the scope) the poured ethanol "rubbing" alcohol (99%) on the paper towel, then lifted the towels straight up and off. A few more repeats, the last lightly dragging the soaked towel across the mirror and the primary was excellently clean. This is a risky not recommended way to clean the mirror- to all- don't do it. It did save that session that night, the alcohol evaporated, no frost and was super fast. Again, dont do this, to all. But a clean mirror is a must for top views IMHO, and should not be something to be scared of IMHO, if done properly as you say Stu.

Yes. Contrary to some members beliefs I believe that a clean mirror is a must. A dirty mirror not only reduces DSO "contrast" through the eyepiece it adds scatter on bright objects reducing the quality of the view IMHO. Some schools of thought maintain a dirty mirror is fine and brag about how long ago it was cleaned... I do not subscribe to this thought.

Congrats! You will love the capability of this scope!

I just love this statement!

I have to say that your lunar images are excellent, its amazing what your doing with the 114mm newt. With respect to the large central obstruction in the SCT's used for highly successful imaging- the effects of the central obstruction and other things can be dealt with in processing, frequency restoration etc, as you know. The large aperture provides more detail than smaller ones , just the way it is. I'm not saying this for you Neil, as you already know it- I'm hoping the OP @chrispj can sort some of this out from info in the thread.

@John Glad you brought the question back to the forefront. To the Op, as long as your telescope "system" is operating at "1/4" PV you are going to see excellent detail on the moon and planets IMHO. Smooth glass means less scatter, again my opinion. With regard to transmission, yes it matters for DSO. All the losses stack up in the telescope system and mass produced SCT are particularly vulnerable to light loss through lowered transmission. A newt with 2 mirrors and high reflectivity will operate around 94% transmission, good refractors a bit higher, depending on the number of lenses and the quality of coatings.Mass produced SCTs about 85%-88% (Starbright). Most mass produced dobs are at the 1/4 PV mark or better IMHO and good refractors at least this, most likely better. Seeing is usually the limiting factor for lunar/planetary and transparency/darkness limits DSO views. Hope this adds a bit of clarity among the "robust" discussions.

Very nice I wonder how it compares to a 100mm Tak?

What brand of refractor is the 8"?